The new models are already available for purchase from Apple's Web site and its retail stores, with prices ranging from $1,199 for the 21.5-inch iMac to $1,999 for the 27-inch model.

Along with the updated CPUs and the new high-speed data port, the new iMacs sport faster Advanced Micro Devices' graphics processors than their predecessors and integrated FaceTime HD video cameras. Otherwise, little else about the iMac has changed from the previous models that debuted in June 2010. (That includes external design; the 2011 and 2010 models look all but identical.)

Apple's new 27-inch iMac includes two Thunderbolt data ports, in addition to four USB 2.0 inputs and a FireWire 800 port.
Sarah Tew/CNET

The upgrades are in keeping with the rumors that appeared on CNET and elsewhere over the past few months. They also match updates Apple made to the MacBook Pro line earlier this year.

Intel's second-generation Core CPUs, formerly known by the code name Sandy Bridge, bring increased power efficiency over Intel's previous generation of Core CPUs, along with faster performance, particularly from its built-in graphics processing capabilities. While the initial batch of Sandy Bridge-supporting motherboards were recalled due to a flaw in one of the storage processing chips, Intel has since rectified the issue and has resumed shipping.

Thunderbolt, which debuted with the updated MacBook Pros, is also an Intel design and offers a new, bi-directional data port designed to simplify external device connections to laptop and desktop computers. The standard supports both data and video throughput simultaneously with the appropriate connectors. As with the MacBook Pro, the Thunderbolt port on the new iMac replaces the Mini DisplayPort output found on previous generation iMacs.